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1.92 regression: Behavior change in <code>PartialEq</code> impl of <code>BTreeSet</code>?

A-collectionsArea: `std::collections`Area: `std::collections`

A-iteratorsArea: IteratorsArea: Iterators

C-bugCategory: This is a bug.Category: This is a bug.

I-prioritizeIssue: Indicates that prioritization has been requested for this issue.Issue: Indicates that prioritization has been requested for this issue.

P-mediumMedium priorityMedium priority

perf-regressionPerformance regression.Performance regression.

regression-from-stable-to-betaPerformance or correctness regression from stable to beta.Performance or correctness regression from stable to beta.

S-has-bisectionStatus: A bisection has been found for this issueStatus: A bisection has been found for this issue

S-has-mcveStatus: A Minimal Complete and Verifiable Example has been found for this issueStatus: A Minimal Complete and Verifiable Example has been found for this issue

T-libsRelevant to the library team, which will review and decide on the PR/issue.Relevant to the library team, which will review and decide on the PR/issue.

Status: Open.

#149122 In rust-lang/rust;

· theemathas opened on Nov 20, 2025

· 

1.92.0

<code>vec::IntoIter::{nth_back,advance_back_by}</code> creates unaligned reference for ZST with alignment greater than 1

A-alignArea: alignment control (`repr(align(N))` and so on)Area: alignment control (`repr(align(N))` and so on)

A-iteratorsArea: IteratorsArea: Iterators

A-ZSTArea: Zero-sized types (ZSTs).Area: Zero-sized types (ZSTs).

C-bugCategory: This is a bug.Category: This is a bug.

I-unsoundIssue: A soundness hole (worst kind of bug), see: https://en.wikipedia.org/wiki/SoundnessIssue: A soundness hole (worst kind of bug), see: https://en.wikipedia.org/wiki/Soundness

P-highHigh priorityHigh priority

T-libsRelevant to the library team, which will review and decide on the PR/issue.Relevant to the library team, which will review and decide on the PR/issue.

Status: Open.

#148682 In rust-lang/rust;

· theemathas opened on Nov 8, 2025

core::Zip::next_back() slow for iterators of different lengths

A-iteratorsArea: IteratorsArea: Iterators

C-optimizationCategory: An issue highlighting optimization opportunities or PRs implementing suchCategory: An issue highlighting optimization opportunities or PRs implementing such

T-libs-apiRelevant to the library API team, which will review and decide on the PR/issue.Relevant to the library API team, which will review and decide on the PR/issue.

Status: Open.

#147704 In rust-lang/rust;

· Dan54 opened on Oct 14, 2025

failed deinterleaving autovectorization

A-autovectorizationArea: Autovectorization, which can impact perf or code sizeArea: Autovectorization, which can impact perf or code size

A-iteratorsArea: IteratorsArea: Iterators

C-bugCategory: This is a bug.Category: This is a bug.

I-slowIssue: Problems and improvements with respect to performance of generated code.Issue: Problems and improvements with respect to performance of generated code.

T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.Relevant to the compiler team, which will review and decide on the PR/issue.

Status: Open.

#146336 In rust-lang/rust;

· edwloef opened on Sep 8, 2025

<code>Vec::into_iter().flatten().collect::&lt;Vec&lt;_&gt;&gt;()</code> doesn't reuse allocation

A-iteratorsArea: IteratorsArea: Iterators

C-optimizationCategory: An issue highlighting optimization opportunities or PRs implementing suchCategory: An issue highlighting optimization opportunities or PRs implementing such

I-slowIssue: Problems and improvements with respect to performance of generated code.Issue: Problems and improvements with respect to performance of generated code.

needs-triageThis issue may need triage. Remove it if it has been sufficiently triaged.This issue may need triage. Remove it if it has been sufficiently triaged.

T-libsRelevant to the library team, which will review and decide on the PR/issue.Relevant to the library team, which will review and decide on the PR/issue.

Status: Open.

#146270 In rust-lang/rust;

· nazar-pc opened on Sep 6, 2025

repeat_with() can return Iterator + Copy

A-iteratorsArea: IteratorsArea: Iterators

C-bugCategory: This is a bug.Category: This is a bug.

T-libsRelevant to the library team, which will review and decide on the PR/issue.Relevant to the library team, which will review and decide on the PR/issue.

Status: Open.

#145603 In rust-lang/rust;

· dohse opened on Aug 19, 2025

<code>String.extend(repeat_n(...))</code> could optimize better

A-iteratorsArea: IteratorsArea: Iterators

A-strArea: str and StringArea: str and String

C-optimizationCategory: An issue highlighting optimization opportunities or PRs implementing suchCategory: An issue highlighting optimization opportunities or PRs implementing such

T-libsRelevant to the library team, which will review and decide on the PR/issue.Relevant to the library team, which will review and decide on the PR/issue.

Status: Open.

#145434 In rust-lang/rust;

· DaniPopes opened on Aug 15, 2025

The <code>Zip</code> iterator does not update the underlying iterator correctly in its <code>TrustedLen</code> specialization.

A-iteratorsArea: IteratorsArea: Iterators

A-specializationArea: Trait impl specializationArea: Trait impl specialization

C-discussionCategory: Discussion or questions that doesn't represent real issues.Category: Discussion or questions that doesn't represent real issues.

T-libsRelevant to the library team, which will review and decide on the PR/issue.Relevant to the library team, which will review and decide on the PR/issue.

Status: Open.

#144012 In rust-lang/rust;

· theemathas opened on Jul 16, 2025

zip(chain(...)) with iterators optimizes very poorly

A-iteratorsArea: IteratorsArea: Iterators

C-optimizationCategory: An issue highlighting optimization opportunities or PRs implementing suchCategory: An issue highlighting optimization opportunities or PRs implementing such

I-slowIssue: Problems and improvements with respect to performance of generated code.Issue: Problems and improvements with respect to performance of generated code.

T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.Relevant to the compiler team, which will review and decide on the PR/issue.

T-libsRelevant to the library team, which will review and decide on the PR/issue.Relevant to the library team, which will review and decide on the PR/issue.

Status: Open.

#143966 In rust-lang/rust;

· The-personified-devil opened on Jul 15, 2025

iter::zip changes vectorization behaviour even if value is unused

A-autovectorizationArea: Autovectorization, which can impact perf or code sizeArea: Autovectorization, which can impact perf or code size

A-iteratorsArea: IteratorsArea: Iterators

C-optimizationCategory: An issue highlighting optimization opportunities or PRs implementing suchCategory: An issue highlighting optimization opportunities or PRs implementing such

T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.Relevant to the compiler team, which will review and decide on the PR/issue.

Status: Open.

#143016 In rust-lang/rust;

· BloodStainedCrow opened on Jun 25, 2025

Performance problem in for loops with step_by(run-time-variable)

A-iteratorsArea: IteratorsArea: Iterators

C-bugCategory: This is a bug.Category: This is a bug.

C-optimizationCategory: An issue highlighting optimization opportunities or PRs implementing suchCategory: An issue highlighting optimization opportunities or PRs implementing such

I-slowIssue: Problems and improvements with respect to performance of generated code.Issue: Problems and improvements with respect to performance of generated code.

T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.Relevant to the compiler team, which will review and decide on the PR/issue.

Status: Open.

#141360 In rust-lang/rust;

· leonardo-m opened on May 21, 2025

The implementation of <code>InPlaceIterable</code> for <code>Flatten</code>&amp;<code>FlatMap</code> is unsound

A-iteratorsArea: IteratorsArea: Iterators

C-bugCategory: This is a bug.Category: This is a bug.

I-unsoundIssue: A soundness hole (worst kind of bug), see: https://en.wikipedia.org/wiki/SoundnessIssue: A soundness hole (worst kind of bug), see: https://en.wikipedia.org/wiki/Soundness

T-libsRelevant to the library team, which will review and decide on the PR/issue.Relevant to the library team, which will review and decide on the PR/issue.

Status: Open.

#135103 In rust-lang/rust;

· steffahn opened on Jan 4, 2025